1. Field of the Invention
The present invention is directed to a method for generating a combined parameter map from a number of individual, initial parameter maps that contain values of various parameters dependent on the position. The invention also is directed to a corresponding apparatus for generating such a combined parameter map.
2. Description of the Prior Art
In an examination of a subject, for example a person or a body part or organ of a person, with an imaging modality, for example with an X-ray device, a computed tomography system, a magnetic resonance tomography system or a sonography device, physical and/or physiological parameters can be obtained from an individual image or from a series of images in addition to the presentation of purely anatomical information. Typical examples of such parameters in an examination supported by contrast agent are the time curve or the maximum value of the contrast agent concentration in specific regions of an examined organ. A signal value can be determined for every individual picture element from the image or image sequence for each parameter of interest, and a parameter map thus can be generated for each of the parameters. For the presentation of the parameter map, the identified values usually are converted into an intensity value with a specific value range, for example between 0 and 4095. This intensity value then can be encoded in a grayscale or color scale for presentation, so that a black-and-white parameter map with various gray gradations or a chromatic parameter map arises.
In many instances, however, a dependable diagnosis is only possible when the behavior of the regions under examination in the examination is observed with respect to various parameters. Thus, for example, an unusual behavior with respect to one parameter can elicit the suspicion that a malignant lesion could be present in the appertaining region of the examination subject. In order to confirm or dispel the suspicion, the behavior of the suspicious region with respect to other parameters must be known. In order to arrive at a dependable conclusion, the examination personnel consequently must monitor a number of parameter maps simultaneously, with subjective perceptions of the examination personnel entering into consideration in borderline cases. A combination of the parameters in a parameter map therefore would facilitate the evaluation of the information.
Conventionally only the possibility of combining a maximum of two parameters in a parameter map has existed, i.e. a combined parameter map can be generated from a maximum of two “initial parameter maps” each respectively representing the values for one parameter with the values of one of the parameters being encoded as color values and the values of the other parameter being encoded as brightness values. A combination of an arbitrary number of different parameters in a single parameter map is not possible with this method.